Maxima Function
fib (n)
Returns the n'th Fibonacci number.
fib(0) equal to 0 and fib(1) equal to 1,
and
fib (-n) equal to (-1)^(n + 1) * fib(n).
After calling fib,
prevfib is equal to fib (x - 1),
the Fibonacci number preceding the last one computed.
(%i1) map (fib, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]); (%o1) [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]